Question

Background

Detectors are called large detector sin a photon-irradiated medium if the detector dimensions relative to the range of the secondary electrons are large.
Detectors that are small compared to the electron ranges and act as senses for the electron fluence existing in the undisturbed medium (Bragg-Gray cavities) vs. detectors that are large compared to the electron ranges and in which CPE is established (photon radiation only). For intermediate situations, neither of the above cases results in a god approximation of the ratio of D/D. Burlin introduced its theory to fill the gap. In the simplest form, the Burlin General

Cavity Theory is written as ???? = [??? (?Δ)??? + (1 − ???) (???)??? ], where ??? is a ???? ? ??? ? ???

weighting factor between 1 (small cavity, Bragg-Gray) and 0 (large cavity, photon-detector), ???? is the dose in the cavity, ???? = (???)??? is the absorbed dose in medium under CPE,

(?Δ)??? is the Spencer-Attix mass electronic stopping-power ratio detector-to-medium (i.e., ? ???

that restricted to losses less than Δ; Δ is chosen such that an electron of this energy has a range just sufficient to cross the cavity i.e., all energy losses are treated as local - for air

cavities used in radiotherapy, around 10 ???) and (???)??? the corresponding mass energy-

absorption coefficient ratio.

? ???

(a) Consider a LiF TLD in a photon radiation field. Is its response energy-dependent and, if so, to which extent when compared to a silicon dosimeter and a diamond dosimeter? Assume the TLD is large (so that Burlin ??? = 0). And if the TLD is small?

(b) Suppose the TLD has, for radiation fields produced by photons with energy 0.2 ??? and 1.25 ???, equilibrium-thickness walls of polystyrene and PMMA. What’s the ratio of the average dose in the TLD cavity to that in the cavity under CPE conditions, assuming Burlin ??? = 1 and Burlin ??? = 0?

(c) Suppose that the TLD, now a LiF cavity enclosed in Al equilibrium-thickness walls, is placed in a radiation field produced by a 6 ??? photon beam and, under CPE conditions, measures 30 ??.
What’s the dose to silicon? Assume the TLD is

(i) small (so that Burlin ??? = 1), (ii) large (so that Burlin ??? = 0). Neglect x-ray attenuation.

(d) When x-ray attenuation cannot be neglected?

Answer 1

TLD stands for thermoluninense dosimeter which gives information of material after irradiated to a radiation.

A) yes TLD is energy dependent. it depend on defect states in material and its is considered high for material with impurity or dopping. in case of silicon and diamond, diamond can have large TL intesity as its band gap is high and absorve radiation of more energy. if TLD is large than the material have deep defet levels as compared to material which TL is small.

B)